Plowing action in a snowplow (or other type of plow) is generally effected by the plowing vehicle's moldboard, the (usually curved) shovel-like blade situated in front of the plowing vehicle. At the lower edge of the moldboard, a sacrificial cutting edge is usually provided—a strip of hardened steel, generally carbide steel, which is bolted to the bottom of the moldboard and which is intended to bear the brunt of the wear (rather than the moldboard itself) as the cutting edge scrapes along the roadway. Exemplary cutting edges can be seen, for example, in U.S. Pat. Nos. 3,477,149; 3,888,027; and 4,590,694. In some cases, cutting edges may take forms other than blades, e.g., they may assume wedge or block shapes, as in U.S. Pat. Nos. 1,543,222; 5,471,770; and 5,611,157; or they may assume the form of flexible teeth, as in U.S. Pat. Nos. 5,140,763 and 5,819,443; or the form of a flexible strip, as in U.S. Pat. No. 2,061,585.
Because such cutting edges wear quickly—they may require replacement in no more than about 100 hours of plowing—there is a significant desire in the road machinery industry to develop ways to reduce cutting edge wear and replacement cost/time. Cutting edges are sometimes protected against impact damage by hinging them to the bottom of the moldboard and then biasing them with springs (as in U.S. Pat. No. 5,437,113), elastic elements (as in U.S. Pat. Nos. 4,347,677; 4,288,932; 5,743,032; 6,125,559; and 6,269,556, as well as in UK Patent GB1058602; Soviet patent SU751891; and French patent FR1243526), or a combination of these (as in German publication DE3205973A1) to remain in their operative position until an object (such as a curb) is struck, in which case the cutting edge will temporarily fold back, to return when the load is relieved. However, these “trip” cutting edge arrangements merely protect against impact damage; ordinary wear from scraping against the roadway is not relieved. Apart from generating undesirable costs from the standpoint of the material cost of blade replacement, the need to replace a worn cutting edge also generates significant costs in terms of lost usage of plowing vehicles, and time lost by plowing personnel to maintenance rather than to plowing operations. In the snowplowing field, where the economic cost of unplowed roads (and the resulting delays in transportation and commerce) can be very significant, lost time is a critical concern. One approach that is often taken is to provide replaceable “teeth” or inserts, often made of specially-chosen materials, at the bottom of the cutting edge so that the teeth can be replaced as they wear. See, e.g., U.S. Pat. Nos. 3,529,677; 3,934,654; 4,715,450; 4,770,253; 5,224,555; 5,778,572; 5,813,474; 5,881,480; 6,003,617; and 6,202,327. While these often allow a cutting edge to last longer, they may nevertheless exacerbate disadvantages in replacement costs and maintenance time.
A hybrid approach is presented by U.S. Pat. No. 5,746,017 to Marvik, wherein the cutting edge is segmented into a number of individual “shares,” and the shares are then embedded side-by-side in an elastomeric mass which is in turn bolted to the lower edge of the moldboard. In effect, the shares resemble a series of “teeth” protruding from an elastomeric “gum” at the bottom of the moldboard. As the shares scrape along the ground, their elastomeric mounting allows each to slightly give when road irregularities are encountered. According to distributors of this type of cutting edge—which is sometimes referred to as the JOMA cutting edge—good snow and ice removal is obtained, and at the same time the shares experience less wear. Wear on the roadway is also reduced, which is an important consideration owing to the cost of replacing scraped-away markings on the roadway, etc. Another advantage reported by users of this type of cutting edge is that the cutting edge transmits substantially less road vibration to the frame and cab of the plowing vehicle, which also results in decreased vehicle wear and maintenance (and is also far less taxing on the plowing vehicle's operator during plowing operations).
However, a significant disadvantage of the JOMA cutting edge is its cost: the expense of generating the multi-part segments or “shares,” and embedding them within an elastomer mount, is significantly greater than the cost of a standard one-piece, all metal cutting edge. Replacement costs can also be effectively exacerbated since when the cutting edge loses one of its “teeth” (shares), the entire length requires replacement for effective cleaning of the surface being plowed. Therefore, it would be useful to have available other cutting edges which obtain results at least comparable to the JOMA, at lesser cost.